Input: sh_keysc - switch to threaded IRQ handler

Update the KEYSC driver to make use of threaded IRQs with IRQF_ONESHOT
to improve interrupt latency. The driver is using udelay() in the ISR
to make sure the hardware has stabilized. Without using interrupt threads
this delay may affect the latency of the rest of the system.

Also pass dev_name() as string for /proc/interrupts.

Signed-off-by: Magnus Damm <damm@opensource.se>
Signed-off-by: Dmitry Torokhov <dtor@mail.ru>